Existing hard disk drives have used continuous media with a recording magnetic film uniformly and continuously sputtered thereon; however, attention is being given to patterned media as a next generation technology for writing and/or reading data at a higher recording density. Patterned media are media with physically separated recording tracks and/or bit patterns formed on its storage surface. In comparison with the recording performance of the existing continuous media, the patterned media provide advantages through improvements in recording transition shape, a reduction in media noise at edges of recording tracks, a reduction in crosstalk from adjacent tracks, and other effects. However, the timing to start writing and reading is determined depending on the patterned media, and therefore magnetic recording/reproducing devices using patterned media are required to have a more precise write timing control function than that of magnetic recording/reproducing devices using conventional existing media.
When a magnetic recording/reproducing device using an existing continuous medium writes data, the device writes patterns, called “preamble” and synchronization or “sync,” for adjusting read frequencies and phases at the beginning of a data sector in which the data is written, and subsequently writes a data pattern. Since the frequency (clock) and phase of the data pattern to be written are not obtained from feedback on the rotational speed variable of the medium and the relative position between the head and medium, the data bits are not always written on precisely the same position on the medium. In other words, the writing operation of data is not synchronized with the medium at the bit level. On the other hand, the reading operation is performed by adjusting a reproduced clock and phase with the use of the preamble and sync patterns written in the beginning of the data sector.
In contrast to this, a magnetic recording/reproducing device using a patterned medium with physical bit formed thereon is used to synchronize with the bit pattern on the medium with great precision in order to write and read data. One of these approaches is disclosed in Japanese Patent Office (JPO) Pub. No. 2004-199806 representing a method for pre-patterning timing marks for writing on media. A method for adjusting the phase of a medium and a recording pattern is disclosed in JPO Pub. No. 2006-164349, which presents a method for learning and determining the time (phase) between the pre-patterned timing mark and the starting point of writing.
Further increases in the capacity of a hard disk device using patterned media necessarily involve the aforementioned precise writing synchronization between patterns on the media and the head. The writing timing synchronization with the media mainly needs two adjustments: a write/read frequency adjustment for compensating write/read frequency fluctuations caused by the rotational speed fluctuations of the medium, the variations in bit patterning apparatuses and so on; and a phase adjustment for compensating the starting point of bits.
In addition, general hard disk devices employ zone formatting for the purpose of allocating a large volume of data. This is a format in which a storage medium is divided along the radius into a plurality of areas (zones), each having a different write frequency and recording density. Typical storage media has a higher recording density and a lower write frequency toward the radially inner zones and a lower recording density and a higher write frequency toward the radially outer zones. This is because the relative linear velocity of the medium to the head decreases toward the radially inner zones and therefore those zones are less affected by band noises, while the relative linear velocity increases toward the radially outer zones and therefore those zones are more affected by band noises. The frequency of the data pattern formed on such a zone-formatted patterned medium discretely changes at its zone boundaries. Also, the head used for the patterned media includes a write element and a read element separated from each other. The write element and read element rotating around a shaft while moving along the radius over the medium possibly involve radial misalignment between the write head and the read head according to where they are positioned on the radius. Due to this, even when the write head is positioned on a track to be written with data, the read head reads information on a different track. If, in order to synchronize the bit pattern on a medium with the writing position of a head, for example, a pattern for providing write timing is formed on the medium upon the manufacture of the medium and signals are reproduced from the pattern to adjust the write timing, as disclosed in JPO Pub. No. 2004-199806, the bit frequency of a recording track in the vicinity of a zone boundary differs from the frequency and phase of the signals reproduced at a position where the read head is currently positioned, and therefore proper writing is impossible.
Therefore, it would be beneficial to have a hard disk device which can use a patterned medium enabling highly-precise control and zoned-bit recording, which alleviates the problems generally associated with such media usage.